1. Field of the Invention
The present invention relates to an uninterruptible power supply device having an AC/DC converter that converts input alternating current power to direct current power and supplies it to a load combined with a battery for backup, and particularly relates to an uninterruptible power supply device that enables automatic reactivation even when the AC/DC converter is stopped due to a protection operation against surge or the like upon alternating current power turn-on.
2. Description of the Related Arts
Conventionally, for example, the device of FIG. 1 is known as an uninterruptible power supply device built in a small private branch exchange.
In FIG. 1, the uninterruptible power supply device 200 has an AC/DC converter 202, and a power factor improving circuit (PFC: Power Factor Controller) 204 and a DC/DC converter 206 are provided in the AC/DC converter 202. The AC/DC converter 202 is supplied with AC 100 volts or AC 200 volts when an AC plug 208 is inserted into an electrical outlet of an AC line, and improves the power factor to “1” so as to reduce noise relative to the outside when the phases of the voltage and the current are tuned by the power factor improving circuit 204. The power factor improving circuit 204 uses, for example, a step-up inverter, and therefore the direct current output voltage is generally DC 240 volts or 480 volts. The DC/DC converter 206 stabilizes input direct current power to DC power having a constant voltage such as DC 24 volts or DC 48 volts required for an exchange. A battery 212 for power-outage backup is connected to the output of the AC/DC converter 202 via a switch 210 that is to be turned off when the battery voltage is reduced to below a specified voltage, and it is charged by the output of the AC/DC converter 202. In the secondary side of the AC/DC converter 202, a DC/DC converter 214 is further provided, and, for example, DC 24 volts, DC 5 volts, and DC 3.3 volts required for exchange circuits are stabilized and output. In such uninterruptible power supply device 200, when power outage of the AC power supply of the electrical outlet to which the AC plug 208 is connected occurs or when the AC plug 208 is pulled out in accordance with needs during usage of the exchange, it is switched to supply of the direct current power from the battery 212, and power supply can be maintained. The battery 212 can serve as a backup up to several tens of minutes to several hours during power outage; however, when the time of power outage is long, a transportable diesel engine generator or the like sometimes substitutes for a commercial power supply in order to realize a further long operation. For example, electrical equipment installed in a building or the like has to be periodically inspected. Power outage is sometimes caused for a long time such as for eight hours for the inspection, and back up by the battery 212 is difficult. Therefore, a transportable diesel engine generator is brought in and activated upon power outage, and it is used by inserting the AC plug of the exchange into the electrical outlet of the diesel engine generator.
However, in such conventional uninterruptible power supply device, when the diesel engine generator is prepared upon prolonged power outage, the AC plug of the uninterruptible power supply device is inserted into a connector of the diesel engine generator, and the diesel engine is activated, there has been a problem that the power supply by the battery is continued and the functions of the exchange are suddenly stopped due to battery exhaust even though AC power is supplied from the generator. Such an abnormal situation is caused when distortion is generated in the sine wave of alternating current power due to an inrush current or the like that flows through another device connected to the connector at the same time upon activation of the diesel engine generator, a surge voltage is applied to the AC/DC converter 202, and protection circuits of the power factor improving circuit 204 and the DC/DC converter 206 constituting the AC/DC converter 202 detect the overcurrent or overvoltage due to the surge and stops the operation. There is a problem that the battery 212 is exhausted in this state to stop the exchange, and considerable damage is caused along with stoppage of the exchange. Particularly, since the exchange is stopped even though it is backed up by operating the diesel engine generator, determining the cause takes labor hour and time, and there is a risk of further damage due to the stoppage of the exchange.